Fixing the `is_dark` method to accept degree units.
Fixing the `is_dark` method to accept degree units.

joshwalawender/POCS,AstroHuntsman/POCS,AstroHuntsman/POCS,AstroHuntsman/POCS,panoptes/POCS,joshwalawender/POCS,panoptes/POCS,panoptes/POCS,panoptes/POCS,AstroHuntsman/POCS,joshwalawender/POCS